Transformist1, this is way past my area of expertize (a very small area), but I just read here ASUS Transformer Pad Infinity bootloader unlock released - Liliputing that "...this unlock will only work on Ice Cream Sandwich. So if the Jelly Bean update ASUS promised comes through, don’t install it if you plan to go through the bootloader unlocking process." This may be your problem! Since no one has responded to your predicament since yesterday morn, I'm going to move this thread to 300 Development, that's where this kind of hanky panky goes on, so you might get some help there. I also changed the title to reflect your problem. Good luck!

Transformist1, this is way past my area of expertize (a very small area), but I just read here ASUS Transformer Pad Infinity bootloader unlock released - Liliputing that "...this unlock will only work on Ice Cream Sandwich. So if the Jelly Bean update ASUS promised comes through, don’t install it if you plan to go through the bootloader unlocking process." This may be your problem! Since no one has responded to your predicament since yesterday morn, I'm going to move this thread to 300 Development, that's where this kind of hanky panky goes on, so you might get some help there. I also changed the title to reflect your problem. Good luck!

Dear sculptedstylus,

First of all thank you very much for your reference !!

The thread you've linked, is for the Infinity (TF700), and not for my TF300, so I'm not sure it is directly connected, but thank you for it anyhow.

I'm not sure really sure that the unlock process was the trigger for the brick (because it worked for few days perfectly, until I've downloaded few programs from Google Play), but I trust you regarding the thread name.

Anyway, thank you so much for escalating this issue, it's not possible that I'm the only one in the world that suffers from this problem !!

Again the issue in 2 line description:Transformer TF300T with stock JB 4.1.1.

Official ASUS unlock tool went well, the device worked for few days after the unlock.

After downloading and running few unknown apps from the Google Play, the device rebooted, and from then stuck on the "ASUS" logo screen.

No fastboot, no RCK, no response for "Power+Volume Down".

Only APX mode (Volume Up) is responding.

Just as an idea for possible solution, I saw a solution for unbrick via APX mode for TF101, with a tool called "EasyFlasher"...